ILL-FATED: Mary Claire Walker (above) and Xiaolu Yu (inset) had consensual sex in 2012 and she accused him of misconduct a year later, his suit says. Photo: Steve Aulenback/Sports Graphics

A former Vassar College student who claims he lost his virginity to a fellow member of the rowing team sued the school yesterday for giving him the boot after she accused him of rape a year later.

Xiaolu “Peter” Yu says he and Mary Claire Walker engaged in “clearly consensual sexual activity” during a dorm-room romp last year, and that she sent him a Facebook e-mail the day after their one-night stand saying she “had a wonderful time.”

But Yu, a standout student from China, says he later got expelled on Walker’s “flimsy say-so,” alleging that male students at the formerly all-women’s college in Poughkeepsie are “invariably found guilty” when accused of sexual misconduct.

According to court papers, Yu and Walker — whose father is a longtime Vassar geology prof — hooked up after an “on-campus rowing-team party” on Feb. 18, 2012.

They headed off to Matthew’s Mug, the school’s popular nightspot, where they made out together, the suit says.

Walker allegedly “agreed to leave The Mug to have sex” with Yu, and they went to his dorm room after she couldn’t find out if her roommate was home.

Once there, Yu told Walker “that it was ‘his first time,’ and she responded, ‘It’s okay, I know what to do,’ ” the suit says.

Walker gave him oral sex, saying, “I know how to do this; I have done this before,” according to the suit.

Later, Walker put a condom on Yu and they got down until his roommate unexpectedly showed up, after which Walker “began to lament about her ex-boyfriend and stated that she was not ready to jump into ‘anything new,’ ” then got dressed and left after noting how she “took Peter Yu’s virginity,” the suit says.

Yu says he later learned that two other women on the rowing team — including his “former romantic interest” — had tried to contact campus security after seeing him walking with Walker, “who appeared to be drunk.”

Walker didn’t respond to a request for comment through her mom, and a college spokesman said that “all student-conduct matters at Vassar are confidential.”

“Our student-conduct policies and procedures are closely reviewed by our attorneys, so they have strong legal grounding, and they’re also designed to consider the rights of all parties in matters like these,” spokesman Jeff Kosmacher added.